Publications

Parametric Oscillation, Frequency Mixing, and Injection Locking of Strongly Coupled Nanomechanical Resonator Modes

Enforcing discipline on nanomechanical vibration

When one strongly shakes a pendulum close to its resonance frequency, it eventually locks to the shaking, i.e. tightly follows the applied force. Here we investigate such phenomena for two orthogonal vibrations of a nanomechanical string resonator which is five hundred times smaller than a human hair and embedded in an all…

Acoustic waves undetectable by transient reflectivity measurements

In laser ultrasonics, ultrashort light pulses generate coherent acoustic pulses of picosecond duration via multiple possible physical mechanisms, involving optoacoustic conversion processes. These wide-band GHz acoustic signals are optically detected at the sample surfaces by ultrafast time-delayed probe light pulses. When the coherent acoustic pulses in GaAS are detected via the Brillouin scattering of probe light pulses of 400…

Finite-time Stückelberg interferometry with nanomechanical modes

Stückelberg interferometry describes the interference of two strongly coupled modes during a double passage through an avoided energy level crossing. In this work, we investigate finite-time effects in Stückelberg interferometry and discuss the exact analytical solution of the double passage Stückelberg problem by expanding the finite-time solution of the Landau–Zener problem. Approximating the return probability amplitudes of the…

Quantized Thermal Transport in Single Atom Junctions

Thermal transport in individual atomic junctions and chains is of great fundamental interest due to unique quantum effects expected to arise in them. Here, by employing novel, custom-fabricated, picowatt-resolution calorimetric scanning probes, we measure the thermal conductance of gold and platinum metallic wires down to single-atom junctions. Our work reveals that the thermal conductance of gold single atom junctions is quantized at room…

Correlation Driven Transport Asymmetries Through Coupled Spins in a Tunnel Junction

Spin–spin correlations are fundamental to many material properties because they favor certain ground states and are key in numerous models that describe the behavior of strongly correlated materials. While the sum of collective correlations usually lead to a macroscopically measurable change in properties, a direct quantification of correlations in atomic scale systems is difficult.
Using a scanning tunneling…

Redox-Active Tetraruthenium Macrocycles Built from 1,4-Divinylphenylene-Bridged Diruthenium Complexes

Metallamacrocylic tetraruthenium complexes were generated by treatment of 1,4-divinylphenylene-bridged diruthenium complexes with functionalized 1,3-benzene dicarboxylic acids and characterized by HR ESI-MS and multinuclear NMR spectroscopy. Every divinylphenylene diruthenium subunit is oxidized in two consecutive one-electron steps with half-wave potential splittings in the range of 250 to 330…

Sub-cycle optical phase control of nanotunnelling in the single-electron regime

The high peak electric fields provided by single-cycle light pulses can be harnessed to manipulate and control charge motion in solid-state systems, resulting in electron emission out of metals and semiconductors or high harmonics generation in dielectrics. These processes are of a non-perturbative character and require precise reproducibility of the electric-field profile.
Here, we vary the carrier-envelope phase…

Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic…

Stimulated Raman scattering microscopy by nyquist modulation of a two-branch ultrafast fiber source

A highly stable setup for stimulated Raman scattering (SRS) microscopy is presented. It is based on a two-branch femtosecond Er:fiber laser operating at a 40 MHz repetition rate. One of the outputs is directly modulated at the Nyquist frequency with an integrated electro-optic modulator (EOM). This compact source combines a jitter-free pulse synchronization with a broad tunability and allows for…